Spin-Imbalance and Magnetoresistance in Ferromagnet/Superconductor/Ferromagnet Double Tunnel Junctions

TL;DR

This paper presents a theoretical study of spin-dependent transport in ferromagnet/superconductor/ferromagnet junctions, revealing how bias voltage can control superconductivity and tunnel magnetoresistance through spin imbalance effects.

Contribution

It introduces a new theoretical framework for understanding how spin imbalance affects superconductivity and TMR in double tunnel junctions under bias voltage.

Findings

Spin imbalance suppresses superconductivity at a critical voltage.

Bias voltage can control tunnel magnetoresistance.

Method for measuring ferromagnetic spin polarization.

Abstract

We theoretically study the spin-dependent transport in a ferromagnet/super- conductor/ferromagnet double tunnel junction. The tunneling current in the antiferromagnetic alignment of the magnetizations gives rise to a spin imbalance in the superconductor. The resulting nonequilibrium spin density strongly suppresses the superconductivity with increase of bias voltage and destroys it at a critical voltage Vc. The results provide a new method not only for measuring the spin polarization of ferromagnets but also for controlling superconductivity and tunnel magnetoresistance (TMR) by applying the bias voltage.